1. Field of Invention
The present invention relates to the field of devices for destroying subsea objects likely to present a hazard for navigation, for example mines.
2. Description of Related Arts
Two main types of mines are known: sea-bed mines which rest on the sea bed, and moored mines which are held by a “mooring” rope to a kentledge. Sea-bed mines are destroyed by deploying an explosive charge called “warhead” in the immediate proximity of the subsea object and exploding it. This method entails marking the mine then bringing the warhead nearby and finally causing the explosion, unlike the dragging of mines that normally is based on magneto-acoustic and/or mechanical means to trigger the mines or cut their mooring rope.
The known methods of destroying a sea-bed subsea mine comprise a step for detecting and/or identifying the mine and a step for destroying the mine using a large explosive charge, of the order of 50 to 100 kg for example, placed at a distance of a few meters from the mine to be destroyed, by means of a subsea craft, normally remote controlled. After having recovered the subsea craft on board a mine-sweeping surface vessel, the mine is destroyed by causing the charge to explode, the shockwave of which causes the mine to explode by its influence. Moored mines are destroyed using a similar method of detection and/or identification which is followed by a step which consists in hooking a squib onto the mooring rope which is placed by means of a remote-controlled or wire-guided subsea craft. Here, too, after having recovered the subsea craft, the pyrotechnic actuation of the squib is provoked by remote control from the surface vessel. The mine returns to the surface and is destroyed by an ancillary means such as a gun. Now, modern sea-bed mines may no longer explode by influence and the destruction by gun of floating moored mines that have been cut or mines drifting on the surface can be difficult because of choppy sea and/or poor visibility. It is therefore necessary to position the warhead very accurately relative to the mine to ensure its destruction. This is also true for the moored mines that are to be destroyed directly, which is relatively difficult, particularly where there are underwater currents. Furthermore, recovering the subsea craft takes time.
Various types of remote-controlled or wire-guided subsea craft are known, in particular from the patents published by ECA, particularly FR-2 684 951 and EP-0 612 656.
Among these craft, there are also consumable craft.
Conventional single-body craft do not allow for objects to be observed and then attacked from above, from below or from the side, unless they have a propulsive architecture that enables the craft to be directed. This leads to the presence of a large number of propulsive units, which considerably increases the cost of the craft. Even provided with numerous propulsive units, the craft cannot work at large angles of inclination, of the order of 50 to 60°, or above. This is all the more true in the presence of sea currents, where such a craft will have great difficulty in maintaining its stability and holding its position.
Document WO 01/38169 (ECA) discloses a mine neutralizing submersible craft, comprising a first part provided with a propulsive unit and a second part that pivots relative to the first and comprising a warhead and at least one sensor for detecting the subsea object so that the warhead and the sensor are oriented similarly relative to a subsea object. The warhead is positioned correctly relative to the subsea object once it is located, hence a better effectiveness.
However, the applicant has realized that the pivoting of the second part would risk modifying the hydrodynamic characteristics of the craft and, as a consequence, provoke an undesirable movement of the submersible craft relative to the subsea object.